Field of the Invention
The present invention relates to a solid fuel. More specifically, it relates to a solid fuel which makes effective use of waste wood, waste paper, a binder, a form retaining agent and a caloric augmentation agent. Much more specifically, it relates to a solid fuel which makes effective use of wood and paper wastes, a binder, a form retaining agent and a caloric augmentation agent, produces as small an amount as possible of a harmful gas or residue after combustion, has a large calorific value and leads to the suppression of the production of carbon dioxide, especially a solid fuel suitable for use as a fuel for power generation.
Prior Art
Along with the modernization of living, waste products such as wood waste, paper waste and plastics are produced in large quantities from domestic lives, production plants, processing plants, etc. and the disposal of these waste products is now a social problem. Most of these waste products are collected and burnt or buried in the ground. However, the proportion of waste products which are recycled into everyday goods or used as energy sources after they are collected is gradually increasing but still unsatisfactory. Especially parts of waste wood from old houses, thinned wood and used paper have been burnt because the collection and sorting of these waste products cost a great deal and the recycling of these is difficult. Along with the frequent occurrence of a wide-scale disaster which is seemed to be caused by the global warming phenomenon in recent years, each country is trying to suppress the production of carbon dioxide which is one of greenhouse effect gases but it can be said that this is still unsatisfactory. Then, solid fuels making use of wood waste, paper waste and plastic waste are used in power boilers as alternatives to oil and coal but it can be said that their effect of suppressing the production of carbon dioxide is still unsatisfactory.
Meanwhile, Patent Documents 1 to 3 propose the recycling of wood waste, paper waste and plastic waste into a solid fuel.
Patent Document 1 proposes a solid fuel which makes use of used paper and plastic waste. This solid fuel actually comprises 25 to 100 parts by weight of plastic waste based on 100 parts by weight of used paper. Thus, a relatively large amount of plastic waste (20 to 50 wt % of the total) is used. Although this Patent Document 1 teaches that a wood-based waste material may be further used, the amount of the wood-based waste material used in Examples is no more than 10 wt % of the total. The above solid fuel contains plastic waste in a relatively large proportion and therefore, the step of dechlorinating the obtained solid fuel by heating it is required to suppress a trouble caused by the inclusion of polyvinyl chloride at the time of combustion.
Patent Document 2 proposes a solid fuel obtained by pressure bonding together plastics, wood powders, bark and used paper and molding the obtained product into a pellet. Although the amount of the plastics contained in the solid fuel is specified as 10 to 80%, judging from FIGS. 2 to 4, the amount of the plastics is estimated at 30% or more, preferably 50% or more.
Patent Document 3 proposes a method of obtaining a fuel by kneading 5 to 10 parts by weight of a synthetic resin-based waste material with 100 parts by weight of a wood-based waste material and pelletizing the kneaded product. The pellet obtained by this method has a small diameter of about 6 to 12 mm, it cannot be said that the calorific value of the pellet is sufficiently large, and further, its form retention stability is unsatisfactory. Therefore, the pellet is unsuitable for use as a solid fuel for thermal power generation.
Meanwhile, along with the frequent occurrence of a wide-scale disaster which is seemed to be caused by the global warming phenomenon in recent years, each country is trying to suppress the production of carbon dioxide which is one of greenhouse effect gases but it can be said that this is still unsatisfactory. Then, solid fuels making use of wood waste, paper waste and plastic waste are used in power boilers as alternatives to oil and coal but it can be said that their effect of suppressing the production of carbon dioxide is still unsatisfactory.
That is, since plastics are used as a binder and a fuel in the solid fuels proposed by the above Patent Documents 1 to 3, considering that the plastics are produced from oil, these solid fuels are unsatisfactory in the effect of suppressing the production of carbon dioxide.